不同林龄木麻黄人工林生物多样性与土壤养分状况研究

木麻黄（Casuarina equisetifolia）是我国东南沿海海岸防护林骨干树种。本文对广东省茂名市木麻黄防护林开展了不同林龄的种群结构、植物多样性、以及土壤养分特征的研究。结果表明,滨海沙地木麻黄群落在生长过程中有明显的自疏现象,18年林个体数（975株·hm-2）不足3年林个体数一半（2350株·hm-2）,3年至6年龄木麻黄生长最快。调查林地内共有植物27种,其中灌木8种,草本植物18种。随林龄的增长,林下植物种数显著增加,多样性指数、均匀度指数逐步增加,优势度指数下降。林地土壤有机碳、全氮与速效氮供应水平极低;土壤磷供应相对较好,表层有效磷一般高于3.5mg·kg-1。土壤有效养分与植物多样性显著相关,显示养分是植物定居的主要限制因素。结果表明,木麻黄林结构简单,生物多样性低,土壤养分贫乏。

Biodiversity and soil nutrient research of Casuarina Equisetifolia plantation at different stand ages

Casuarina equisetifolia is the main tree species of China＇s southeast coastal shelter forest. In this paper, we studied the community structure, understory species composition, biodiversity, and soil nutrient along a chronological sequence of Casuarina coastal forest shelterbelts. The results show that self-thinning of the Casuarina plantations was very significant. The individual number in the 18-years old plantation is 975 plants·ha-1, which is less than half of the number in the 3-years old plantation（2350plants·ha-1）. The most rapid growth occurred in the 3-6 years stage. The total species number in the investigating area reached 27,including eight shrub species and 18 herb species. With the growth of plantation, the biodiversity index and evenness index gradually increased, while the dominance index decreased. Forest soil organic carbon, total nitrogen and available N content were low, and had no significant relationship with stand age. The phosphorus supply in this sand soil is relatively good, and the concentration of the available P was generally higher than 3.5 mg·kg-1in the surface soil layer. Soil available nutrient had significant relationship with the plant diversity, which showed that the soil nutrient was the main limiting factor of plant colonization. The results indicated that Casuarina equisetifolia plantation has simple forest structure, low biodiversity and poor soil nutrient condition.